The present invention refers to a widened-base structure for supporting a platform for offshore operations, such as well drilling, oil and gas exploration and production, or for support or any other installations at sea, having four main legs and a widened base, endowed with dihedral external lateral faces, in which the main legs, extended by ramifications referred to as secondary legs, make up the launch rails on which the structure can be loaded out in a barge from the construction site and later launched at sea from the barge.
The most commonly employed structures for supporting offshore platforms are space frame with four or eight main legs, such space frames having a pyramidal frustum configuration, with square or rectangular base and top. The choice of a structure having either four or eight legs depends basically on the required base and top sizes as well as on the magnitude of the acting operational and environmental loads, so that when such requisites can be met for a four-legged structure, this is normally the most simple and efficient solution.
The eight-legged structures are normally installed by launching, using as launch rails two parallel internal faces of structure and showing, consequently, few elements specifically designed for the launching operation. As a drawback, they present larger structural complexity, with a larger number of structural elements to be manufactured and assembled, causing an increase in the acting environmental loads.
The four-legged structures are normally installed by lifting or launching, according to their dimensions and weight and the performance of the available naval facilities. When launched, the conventional four-legged structures require specific additional structures, such as two launch trusses or internal members for bearing and sliding, leading effectively to a six-legged structure, wherein the four main legs located at the corners of the structure are basically used to bear the operation and environmental loads while the two parallel internal legs are used only in the installation phase. These additional structures are useless and cumbersome, since they do not contribute to the overall strength and increase the dead weight and environmental loads acting on the structure.